The present invention relates to a tool holder unit for a robot, and more particularly relates to an apparatus for easily and accurately moving a tool held by a robot relative to a workpiece.
One conventional example of such a tool holder unit is disclosed in Japanese Utility Model Laid-open Hel. 2-107416. This tool holder unit includes a device for removing burrs from a workpiece. More specifically, a presser unit holding a tool is supported in a main body of the device and is provided with two sets of drive sources, i.e. hydraulic cylinders. One hydraulic cylinder is operationally connected to the presser unit in the axial direction of the presser unit. The other hydraulic cylinder is operationally connected to the presser unit in a direction normal to the axial direction of the presser unit. The first hydraulic cylinder forces the tool held by the presser unit to advance toward a work, whereas the second hydraulic cylinder forces the tool to recede from the work.
In the case of this prior art device, however, smooth movement of the presser unit is greatly hindered by various factors. First, points of force transmission by the two hydraulic cylinders are separated from each other in a direction normal to the axial direction, i.e. the sliding direction of the presser unit. This arrangement tends to generate a bending moment to twist the presser unit in an axial direction of the presser unit, thereby hindering smooth sliding of the presser unit in the axial direction.
In addition, during operation on the workpiece, reaction force from the workpiece also generates a like bending moment which twists the presser unit around its axial direction, thereby again hindering smooth sliding of the presser unit in its axial direction. Further, sliding resistance by the two hydraulic cylinders also hinders on the sliding movement of the presser unit.